The Wayward Knight

This side quest becomes available after you close the first Oblivion gate in Kvatch. Travel to Cheydinhal and the local townsfolk will tell you that there is an open Oblivion Gate outside of town. If you talk to the Count, he'll tell you that he is too troubled to speak and that all discourse should go through Amminus Gregori. Nobody will tell you who Amminus Gregori is, so you'll have to go look for this Oblivion Gate yourself.

Go outside of Cheydinhal to the west and look for the Knights of the Thorn Lodge. Just nearby is the Oblivion Gate everyone is afraid of. What's more, there are some guards patrolling the area. Go down and talk to them. Speak with Amminus and he'll tell you about the foolish son of the Count named Farwil who went inside the Gate to close it with a small army of wanna-be knights. As soon as you step through the Gate, you'll find one of the dead knights. Things are not looking good for young Farwil.

Continue down the slopes until you find Farwil. Rather than allow himself to be escorted back, he demands that you press onward to close the Gate by taking the Sigil Stone. From this point on, follow whichever tactics you find work best for closing an Oblivion Gate. You are supposed to keep Farwil alive, but it doesn't really matter if he dies. Pull out the Sigil Stone without letting Farwil die and you'll be rewarded with your choice of the Staff of Indarys, which does Shock and Strength damage, or the Thornblade, which does Disintegrate Armor on strike. You'll also get the Knights of the Thorn Medallion which boosts your Speechcraft by 15 points. If Farwil dies, your journal will update and tell you that you should grab his Signet Ring as proof of his death. Take it and the Medallion you would have been rewarded with if he lived off of his body. After you close the gate, return to the Count and tell him the bad news. He'll allow you to keep the ring which is only good for enchanting and will give you 200 Gold as a reward.